A conventional hydraulic pressure brake apparatus generally includes a brake pedal, a master cylinder having a cylinder body formed therein with a cylinder bore and a piston slidably fitted in the cylinder body in such a manner that the piston is moved during depression of the brake pedal and with a pressure chamber being defined in the cylinder bore at the front side of the piston, a plurality of wheel brakes in fluid communication with the pressure chamber to provide braking forces to the respective wheels when a fluid under pressure is applied to the wheel brakes as a result of the depression of the brake pedal, an accumulator for accumulating a high-pressure brake fluid, a first valve for establishing and interrupting fluid communication between the accumulator and the wheel brakes, and a second valve for establishing and interrupting fluid communication between the brake chamber of the master cylinder and the wheel brakes.
This conventional brake apparatus includes two brake operation modes, a normal brake operation mode and an automatic brake operation mode. The normal brake operation mode involves supplying braking pressure generated in the brake chamber of the master brake cylinder to the wheel brakes when the brake pedal is depressed. The automatic brake operation mode involves supplying pressure in the accumulator to the wheel brakes irrespective of operation of the brake pedal by establishing fluid communication between the accumulator and the wheel brakes and interrupting fluid communication between the brake chamber of the master cylinder and the wheel brakes.
In addition, if the brake pedal is depressed while the brake apparatus is in the automatic brake operation mode, the wheel brakes are brought into fluid communication with the pressure chamber by the second valve so that in addition to the pressure in the accumulator applied to each wheel brake, the master cylinder pressure is applied to each wheel brake.
However, in this conventional brake apparatus, to obtain a braking pressure in the wheel brakes when the brake pedal is depressed during the automatic brake operation mode which is substantially equivalent to the braking pressure in the wheel brakes when the brake apparatus is in the normal operation mode, the amount of brake pedal depression (i.e., the brake pedal stroke) is smaller than that in the normal operation mode. These two different amounts of brake pedal depression for obtaining two equivalent or substantially equal braking forces may not provide a good braking feeling.
In light of the foregoing, a need exists for a hydraulic pressure brake apparatus which is able to provide a good braking feeling without the foregoing drawback.